Photocatalytic degradation of NO/NO₂ gas injected into a 10-m³ experimental chamber

This paper investigates a new test method to assess the photocatalytic activity of plasterboards coated with a TiO₂ dispersion under real-world conditions. The degradation of nitrogen oxides NO _x (NO and NO₂) is studied and the photocatalytic efficiency under UV illumination is evaluated in a 10-m³ room after a constant gas injection. Two ultrafine TiO₂ dispersions are used: 0.85% TiO₂ and 5% TiO₂, and three types of gas are tested: an NO/NO₂ mixture (8/8 mol-ppm), NO (45 mol-ppm) and NO₂ (45 mol-ppm). The test method presented here is midway between laboratory and real-scale procedures and allows better control of the experimental parameters than a real field experiment. Testing a mixture of NO and NO₂ is a way to get closer to real-world conditions as air is polluted by various gases. This study focuses on the degradation of NO and NO₂ under UV illumination when two types of TiO₂ dispersions are used and highlights the difference in behaviour between these two molecules in terms of photocatalytic degradation. The results show that photocatalytic activity does not appear to be efficient to degrade NO₂ molecules. Another mechanism seems to be responsible for the reduction of the concentration of NO₂, namely adsorption. Encouraging results are obtained with NO molecules, which can be degraded by photocatalysis. The degradation observed is even greater with the more concentrated TiO₂ dispersion.